The Sure Way to Estimate Quantities
 

PPC Cement for Best Results

When working with cement, it is vital you take into account the different methods of concrete mix estimating and how to calculate concrete quantities. This will ensure your project lasts a lifetime.

To ensure that your mix produces best results, you need to use a power packed cement, like PPC Cement with extra strength. Because it has extra strength it makes more concrete than other regular general purpose cements. So you will achieve more for less.*

*For more details on comparative mixes, see the Affordable Housing page.

PPC Cement Products

PPC SUREBUILD CEM II 42.5 N – This is a general purpose cement for building and civil engineering work. PPC SUREBUILD Cement 42,5 N with extra strength, gives you more concrete than regular 32,5 general purpose cements. PPC OPC CEM I 52.5 N - For use in structural concrete and ready mix concrete and where high early strength is needed. PPC OPC Cement 52,5 N with extra strength gives more yield than regular cements.
The Sure Way To Estimate Quantities The Sure Way To Estimate Quantities

Batching and Mixing Materials

When mixing materials, it is important to know the correct ratios that allow for accurate concrete mix estimating. Below is a breakdown of how to batch and mix different materials:

  • 1 bag of cement has a volume of 33 litres
  • 1 builder’s wheelbarrow has a volume of 65 litres which is equivalent to TWO bags of cement
  • Do not split bags when batching except for small or unimportant work
  • Use a concrete mixer or hand mix on a dry, clean, non-absorbent surface
  • When mixing concrete by hand, first mix the cement, sand and water thoroughly and mix in the stone last – this saves a lot of effort
  • Mix until colour and workability are uniform
The Sure Way To Estimate Quantities
The Sure Way To Estimate Quantities
The Sure Way To Estimate Quantities

*NHBRC guidelines

PPC SUREBUILD Cement 42,5 N Concrete Mixes

Estimating concrete quantities can prove challenging and it’s vital to produce the correct mix for your project. Below is a simple table of best practice amounts and guidelines on how to better calculate concrete quantities.

The Sure Way To Estimate Quantities
The Sure Way To Estimate Quantities
The Sure Way To Estimate Quantities

For all concrete work add sufficient water to make a plastic, workable mix. The addition of too much mixing water will cause segregation and weaken the mix.

Transporting, Placing and Compaction

  • Concrete must be transported from the mixer in such a way as to avoid contamination, loss of paste and segregation
  • Concrete should be placed as near as possible to its final resting place
  • Concrete must be compacted to remove entrapped air which weakens the concrete
  • Concrete may be compacted using hand tools or with mechanical vibrators

Curing of Concrete

  • Concrete gains strength over a period of time by means of chemical reactions between the cement and the mixing water. This is called “hydration”
  • If the concrete is allowed to dry out, hydration will stop and the concrete will not reach its potential strength
  • Curing concrete means to protect it from drying out and is best done by keeping the concrete wet for as long as possible. In practice, the first three days of wet curing are the most important

Storage of Bagged Cement

  • Cement should be stored in a weather proof shed or container
  • It should be closely packed, away from doors and windows
  • It should be packed off the floor, and on plastic
  • It should be covered with a plastic sheet or tarpaulin
  • It should be stored so as to ensure "first in - first out" use

Safety

  • Do not stack bags more than 12 units high
  • Do not stack more than two pallets high
  • Pick up bags correctly to avoid injury
  • Avoid contact with eyes, skin and clothing. Cement and cement paste are highly alkaline and chemical burns may occur

Tips for Using Concrete in an Environmentally Responsible Manner:

  • Use the recommended mix design proportions on the bag to mix the concrete
  • Use the correct strength mix to minimise waste
  • Do not add too much water – this will reduce the concrete strength
  • Mix just enough concrete (mortar or plaster) for your project
  • If you are building a house, make sure you design for optimal energy efficiency
  • Use good quality aggregates and potable water
  • Cure the concrete properly to get maximum durability
  • Do not waste water when cleaning
  • Dispose of your paper bags in a responsible manner
  • Use local raw materials - this reduces the carbon footprint of the transport component
  • Recycle building rubble where possible

For more advice on cement please ask your PPC Cement stockist or call the PPC toll-free help line: 0800 CEMENT (236 368)- SA only.

Click here for this information in downloadable PDF format.